1. Field of the Invention
The present disclosure relates to a method for driving an imaging apparatus having an analog-digital converting unit which converts an analog signal to a digital signal, a method for driving an imaging system, an imaging apparatus, and an imaging system.
2. Description of the Related Art
As an example of imaging apparatuses, an imaging apparatus has been known including pixels which perform photoelectric conversion and output signals based on incident light and a column parallel analog-digital conversion unit (hereinafter, called a column ADC where ADC stands for analog digital converter) having an AD converter at each column of a pixel array having pixels arranged in a matrix form. In the column ADC, the AD converter at each column converts an analog signal (hereinafter, called a pixel signal) output from a pixel to a digital signal.
Japanese Patent Laid-Open No. 2008-136042 discloses an imaging apparatus which AD converts a noise signal output from a pixel and a photoelectric conversion signal based on incident light. Hereinafter, a noise signal and a photoelectric conversion signal will be collectively called a pixel signal. A digital signal based on a noise signal and a digital signal based on a photoelectric conversion signal contain an offset component of an AD converter. Japanese Patent Laid-Open No. 2008-136042 discloses an imaging apparatus which acquires a difference between a digital signal based on a photoelectric conversion signal and a digital signal based on a noise signal in order to reduce an offset component contained in a digital signal based on the photoelectric conversion signal at an AD converter. Thus, the imaging apparatus in Japanese Patent Laid-Open No. 2008-136042 generates a digital signal containing a less offset component of an AD converter.